The invention described herein was made in the course of, or under, a contract with the United States Atomic Energy Commission, and pertains generally to apparatus for monitoring displacements of a reactor core and more particularly to apparatus for monitoring displacements of core components immersed in the liquid metal coolant of a fast breeder reactor.
In nuclear reactors it is desirable to provide an early indication of the displacement of core components in order to avoid abnormal operating conditions. The displacement of core components is usually indicative of a failure of a core support component structure which can cause a blockage of coolant flow, resulting in a rise in core temperature to an undesirable and abnormal level. In the unlikely event of such a failure early detection can enable the plant operator to implement corrective action to avoid operating conditions which might otherwise necessitate the complete shut-down of the reactor system.
State of the art displacement sensors are generally not compatible with in-core monitoring applications for fast breeder reactors, due to the severe high temperatures and the electrically conductive and caustic nature of the sodium coolant.
For example state of the art displacement indicators applied to nuclear reactor applications such as are described in the patents to R. Wildgoose, U.S. Pat. No. 3,296,081 and J. C. Singleton, et al, U.S. Pat. No. 3,492,616, employ magnetically permeable material in combination with a movable piston/cylinder arrangement i.e. linear voltage differential transformers with a movable core, which are not particularly suitable for in-core monitoring applications. This is especially true in liquid metal reactor applications due to the caustic nature of the core environment. Adapting such transducers generally requires a bellows seal to isolate the transducer from the sodium coolant while enabling longitudinal movement of the piston. It is generally accepted that the integrity of such seals is highly susceptable to failure during the desired operating lifetime of up to 10 years. Furthermore, the high temperature experienced in the core of a fast breeder reactor severly degrades the magnetic permeability of the materials employed and thus the detectors response.
While linear differential transformer transducers have been constructed with non magnetic cores such as the transducer described in the patent to Church, U.S. No. 3,484,678, a severe problem still exists in isolating the piston from the core environment while enabling longitudinal movement of the piston shaft, which is used to translate core motion into an electrical output.
Accordingly, an improved reactor core displacement transducer is desired which does not require the use of magnetically permeable material.
Additionally, a new reactor core displacement sensor is desired which can function reliably, totally isolated from the core environment, for extended periods of operation.
Furthermore, a sensor is desired that can be easily removed from its internal core location without the necessity of dismantling the core.